European Green Crabs

At the Friends of Skagit Beaches Annual Meeting this past week, Emily Grason, PhD, came and spoke to us about the European Green Crabs that have been found in our area. She works for WA Sea Grant - a program run by the College of Environment at the University of Washington.

Why is this important?

Because the European green crab is one of the worst invasive species on the planet. They disrupt and threaten our native species habitats - and these little guys aren't ever going to be hunted for their tasty flesh. They are little - think about a woman's fist as the size of the shell at their largest size.

photo by E. Grason

Here's a link to Emily's Crab Team

I've been hearing about the green crabs over the last year - especially last summer when 4 were found in Padilla Bay. The first green crab in the inland waters of the Salish Sea was caught over in Westcott Bay on San Juan Island earlier last year. Link to press release

The European green crab came over to the east coast of the United States early in the 19th century. That population is still increasing its territory. The east coast green crabs were found in San Francisco bay in 1989. They knew where these greens came from due to genetic testing.  It has been theorized that El Nino events in the Pacific have brought the green crabs up the coast to the Pacific Northwest.

It was in 2012 that a well established colony in Sooke Bay was discovered.

The Crab Team started up in 2015 with the goal to use citizen science to monitor habitats that the green crabs like. They have 26 sites up and down the sound with 100 volunteers. The volunteers use baited traps, molt searches and habitat (soils) monitoring.

It's not easy to catch these little guys - and they are little compared to our full-size Dungeness and Rock crabs. They do take over habitats of the little hairy crabs - those muddy, salt water embankments and eel grass beds.

Shore crabs the Hairy shore crab and (bottom) the
Purple shore crab

"Both native shore crabs can be green in color but have only 3 marginal teeth (from eye heading back on the carapace)." - from Crab Team webpage

Crab team gets a lot of calls about our little friends to the left - so its good to know how to identify our native shore crabs against the characteristics of the European green crab - who preys on these guys as well as the juvenile dungeness crabs that like the same habitats for growth and nourishment.

CRAB TEAM ID GUIDE

The green crabs that turned up in Westcott and Padilla bay most likely washed into the Strait of Juan de Fuca about a year ago as a larvae group - possibly from Sooke. It is illegal for ships to clear their ballast tanks in the NW - which is probably how the crabs came across the Atlantic years ago. There isn't any sign of colonies establishing themselves.

Dr. Grason laid out Where Do We Go From Here?

1.  If we do nothing: There is a high likelihood that we will see a hit in our seafood and not just because they are eating little dungeness crabs. Crabs like shellfish - a lot. They also destroy eel grass beds. Our grass is a bit different then what is off the Atlantic, but the damage would still be felt in all the other species that utilize eel grass as a habitat. We're talking forage fish that salmon eat and the other critters up the food chain.
2. How to manage this invasive species: Trapping is still the best option. Some other ideas have been floated that - things like introducing a parasite that stops them from breeding - but unfortunately those options would impact other crabs as well. It was also be helpful if British Columbia @ Sooke took the invasive colony seriously and attempted to control it.
3. Best Next Steps: To continue with volunteer monitoring. She proposes to make sure residents and shellfish growers stay vigilant.

What to do if you think you spot one? TAKE PICTURES ONLY, take down as detailed of location as you can (coordinates on a phone compass are great) and report it to crabteam@UW.edu.